Transaction-Level Modeling (TLM) is a new paradigm for the HW/SW co-design of embedded systems that allows the early development of HW-dependent software running on a fast-executing platform model (before the actual HW design is complete). To be fast, TLM initially abstracts from timing. However, when the model is time-annotated, the early code might not be timeconstraint compliant. We propose a technique that harmonizes the pre-compiled code to the annotated constraints without the need for recompilation. It relies on an automatically retargetable code scheduler. Experimental results show that not only time constraints are efficiently handled, but they are actually exploited for optimization, leading to speed-ups of 1.18 to 1.23 over pre-optimized code.